The purpose of this paper is to develop the systematic method of design for the suspension's hard points which have much influence on the performance of motion of the automotive. The suspension system is kinematically modeled by introducing the composite joints to reduce the mount of calculation, and analyzed in the Cartesian coordinates.
In the sensitivity analysis, the static design parameters, toe angle, camber angle, caster angle, kingpin angle, and roll center height are specified as the target function and the hard points as the design variables. To obtain the analytic sensitivity of the target function, the direct differential method is employed and the partial differentials of the target function with respect to the design variables are derived analytically.
The kinematic sensitivity of the static design parameters could be used in the course of the design change of the suspension system. The sensitivity of the static design parameters could be used in the optimum design of the suspension system as the gradient of the objective function. The result of the optimum design showed improved performance of the suspension system.